import { BackSide, FrontSide, CubeUVReflectionMapping } from '../../constants.js';
import { BoxGeometry } from '../../geometries/BoxGeometry.js';
import { PlaneGeometry } from '../../geometries/PlaneGeometry.js';
import { ShaderMaterial } from '../../materials/ShaderMaterial.js';
import { Color } from '../../math/Color.js';
import { Mesh } from '../../objects/Mesh.js';
import { ShaderLib } from '../shaders/ShaderLib.js';
import { cloneUniforms } from '../shaders/UniformsUtils.js';

function WebGLBackground(renderer, cubemaps, state, objects, premultipliedAlpha) {
  const clearColor = new Color(0x000000);
  let clearAlpha = 0;

  let planeMesh;
  let boxMesh;

  let currentBackground = null;
  let currentBackgroundVersion = 0;
  let currentTonemapping = null;

  function render(renderList, scene) {
    let forceClear = false;
    let background = scene.isScene === true ? scene.background : null;

    if (background && background.isTexture) {
      background = cubemaps.get(background);
    }

    // Ignore background in AR
    // TODO: Reconsider this.

    const xr = renderer.xr;
    const session = xr.getSession && xr.getSession();

    if (session && session.environmentBlendMode === 'additive') {
      background = null;
    }

    if (background === null) {
      setClear(clearColor, clearAlpha);
    } else if (background && background.isColor) {
      setClear(background, 1);
      forceClear = true;
    }

    if (renderer.autoClear || forceClear) {
      renderer.clear(renderer.autoClearColor, renderer.autoClearDepth, renderer.autoClearStencil);
    }

    if (background && (background.isCubeTexture || background.mapping === CubeUVReflectionMapping)) {
      if (boxMesh === undefined) {
        boxMesh = new Mesh(
          new BoxGeometry(1, 1, 1),
          new ShaderMaterial({
            name: 'BackgroundCubeMaterial',
            uniforms: cloneUniforms(ShaderLib.cube.uniforms),
            vertexShader: ShaderLib.cube.vertexShader,
            fragmentShader: ShaderLib.cube.fragmentShader,
            side: BackSide,
            depthTest: false,
            depthWrite: false,
            fog: false,
          }),
        );

        boxMesh.geometry.deleteAttribute('normal');
        boxMesh.geometry.deleteAttribute('uv');

        boxMesh.onBeforeRender = function (renderer, scene, camera) {
          this.matrixWorld.copyPosition(camera.matrixWorld);
        };

        // enable code injection for non-built-in material
        Object.defineProperty(boxMesh.material, 'envMap', {
          get() {
            return this.uniforms.envMap.value;
          },
        });

        objects.update(boxMesh);
      }

      boxMesh.material.uniforms.envMap.value = background;
      boxMesh.material.uniforms.flipEnvMap.value = background.isCubeTexture && background._needsFlipEnvMap ? -1 : 1;

      if (
        currentBackground !== background ||
        currentBackgroundVersion !== background.version ||
        currentTonemapping !== renderer.toneMapping
      ) {
        boxMesh.material.needsUpdate = true;

        currentBackground = background;
        currentBackgroundVersion = background.version;
        currentTonemapping = renderer.toneMapping;
      }

      // push to the pre-sorted opaque render list
      renderList.unshift(boxMesh, boxMesh.geometry, boxMesh.material, 0, 0, null);
    } else if (background && background.isTexture) {
      if (planeMesh === undefined) {
        planeMesh = new Mesh(
          new PlaneGeometry(2, 2),
          new ShaderMaterial({
            name: 'BackgroundMaterial',
            uniforms: cloneUniforms(ShaderLib.background.uniforms),
            vertexShader: ShaderLib.background.vertexShader,
            fragmentShader: ShaderLib.background.fragmentShader,
            side: FrontSide,
            depthTest: false,
            depthWrite: false,
            fog: false,
          }),
        );

        planeMesh.geometry.deleteAttribute('normal');

        // enable code injection for non-built-in material
        Object.defineProperty(planeMesh.material, 'map', {
          get() {
            return this.uniforms.t2D.value;
          },
        });

        objects.update(planeMesh);
      }

      planeMesh.material.uniforms.t2D.value = background;

      if (background.matrixAutoUpdate === true) {
        background.updateMatrix();
      }

      planeMesh.material.uniforms.uvTransform.value.copy(background.matrix);

      if (
        currentBackground !== background ||
        currentBackgroundVersion !== background.version ||
        currentTonemapping !== renderer.toneMapping
      ) {
        planeMesh.material.needsUpdate = true;

        currentBackground = background;
        currentBackgroundVersion = background.version;
        currentTonemapping = renderer.toneMapping;
      }

      // push to the pre-sorted opaque render list
      renderList.unshift(planeMesh, planeMesh.geometry, planeMesh.material, 0, 0, null);
    }
  }

  function setClear(color, alpha) {
    state.buffers.color.setClear(color.r, color.g, color.b, alpha, premultipliedAlpha);
  }

  return {
    getClearColor() {
      return clearColor;
    },
    setClearColor(color, alpha = 1) {
      clearColor.set(color);
      clearAlpha = alpha;
      setClear(clearColor, clearAlpha);
    },
    getClearAlpha() {
      return clearAlpha;
    },
    setClearAlpha(alpha) {
      clearAlpha = alpha;
      setClear(clearColor, clearAlpha);
    },
    render,
  };
}

export { WebGLBackground };
